My requirements for the filament runout sensor enclosure:

1. Easy to print
2. No additional hardware needed
3. Mounted to the printer, not dangling somewhere
4. Wires going out the back to avoid the x-axis
5. Act as a guide so it doesn't put stress on the filament

Buy the cheap micro switches from your favorite provider (I got 10 for $8 from Amazon) and they should plop right in. It's really easy to get going if you're using OctoPrint as the OctoPrint-Enclosure plugin does all the heavy lifting for you. There are several other plugins that exist but seem to no longer be maintained or can't run a GCODE command (e.g. M600 for filament change) when the sensor is tripped.

This was a cheap and fairly easy addition to my Ender 3 Pro, but it should work for most Creality printers with the same extruder setup. I originally had a lidless version, and I've kept that around for posterity's sake. So either use the base and the lid models together or use the originalmodel without the lid by itself. Enjoy!

Tweaked the design by rghawi to meet all my needs. https://www.thingiverse.com/thing:4116904

Octoprint-Enclosure Plugin - https://plugins.octoprint.org/plugins/enclosure/